1. Field of Invention
The proposed invention relates to a non dusty, free flowing, storage stable solid composition. This invention particularly relates to a non dusty, free flowing, storage stable solid composition comprising of at least one pesticide from pyrethroid class like cypermethrin, fenvalerate, permethrin, alphacypermethrin, betacypermethrin, zetacypermethrin, deltamethrin, cyfluthrin, low melting solid pyrethroids like bifenthrin, lambda cyhalothrin, and/or bioresmethrin, more particularly a high viscous liquid insecticide like permethrin. More particularly, this invention relates to a stable composition with improved properties of dispersibility and suspensibility brought about by a combination of inert ingredients silica and kaolin along with block copolymer of ethylene oxide and propylene oxide in specific proportions. The present invention also relates to a process of preparing the said composition.
2. Description of Related Art
Solid compositions like granules are mainly produced by methods such as kneading, extrusion granulation, impregnation, coating etc. Granules are more frequently applied to water surface or soil than directly applied to target crops. After application to water surface or soil, the active ingredient of granules dissolves/disperses in water or vaporizes to reach its action sites and displays the effect. It is therefore required that the same water dispersibility and suspensibility as those at the time of formulation are maintained even after long term storage.
Dry powdery (like wettable powder WP and others) composition has disadvantages like presence of sediment at the bottom of dilution tank, choking of nozzle while spraying, lumping during storage and drift problem at the time of production, packing, transportation, storage, handling, dilution and use.
Generally in liquid formulations like emulsifiable concentrates (EC), soluble liquid (SL), Microemulsions (ME), and capsule suspensions (CS) etc., the composition involves the use of organic solvents like petroleum ether, hydrocarbon solvents, xylene, isopropyl alcohol etc., which may cause further problems like toxicity, irritation to human body and/or other associated problems due to their physico-chemical properties like flash point, solvency with other materials, flammable and reactive nature.
All liquid compositions (like emulsifiable concentrates EC and others) which have been used in agriculture or veterinary applications comprising liquid pyrethroids of concentrations more than 20% suffer with high volatility due to volatile contents and comprise flammable solvents. Organic solvents are most commonly used as inert solvents. Suitable as liquid solvents, are aromatic hydrocarbons, such as xylene, toluene or alkyl naphthalenes; chlorinated aromatic hydrocarbons and chlorinated aliphatic hydrocarbons, such as chlorobenzenes, methylene chloride; aliphatic hydrocarbons, such as cyclohexane or paraffins, for example petroleum fractions, mineral and vegetable oils, alcohols, such as butanol or glycol as well as their ethers and esters, ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone or cyclohexanone; strongly polar solvents, such as dimethylformamide and dimethylsulphoxide. Some of these solvents are agriculturally unacceptable, and need to be used in low or high concentrations to produce formulations of desired strength, which can be diluted and applied to the target areas to control pest effect. Selection and use of the solvent is based on the solubility criteria for active ingredients which sometimes require a single solvent or a combination of solvents as per the type and strength of the formulation product.
WO 9007275, discloses a dry herbicidal composition comprising a water soluble salt of N-phosphonomethylglycine as a water dispersible granule, water soluble granule, water dispersible powder or water soluble powder. The composition comprises a water soluble salt of N-phosphonomethylglycine and additionally one or more liquid surfactants. This invention requires a preparation of herbicidal water soluble salt during the process from its acid derivative (which is solid in physical form) or a water soluble salt (in solid physical form) as one of the main ingredients.
Prior art, Japanese patent 2003095810, discloses the wettable granules comprising liquid pesticidal active ingredient, solvent, emulsifier, dispersion agent and surfactant. This invention requires the use of solvent so that the active ingredient gets uniformly distributed over the inert ingredients.
Also, prior art EP127773, discloses tablet preparation of a pesticidal composition comprising a pesticide, an emulsifier or dispersing agent for the pesticide and a self disintegrating agent capable of effervescing or swelling on being contacted with water. The pesticide disclosed is a synthetic pyrethroid from 1-20% by weight. This invention requires a self disintegrating agent which is capable of effervescing or swelling on being contacted with water. Methylene dichloride is used as a solvent for the active ingredient and the simple mixing process is done to mix a solution of above active ingredient and other ingredients comprising emulsifier or dispersing agent, lubricants, surfactants and antifoaming agents. Then the granule formation is done followed by tablet formation.
The preparation of granules via an extrusion process is well known. Most of the known processes extrude a premix of active material and other ingredients under relatively high pressure, (and generally in excess of 100 psi) and cut the spaghetti like extrudate into short lengths. These may be subsequently dried. An alternative process is disclosed in copending application PCT AU 88/00201 which uses low pressure extrudation (<30 ps of a wet mix having relatively high levels of water. This leads to an extrudate of low compactness which readily breaks into small segments by gentle rolling or tumbling action which also tends to round the ends of the granules. Again these granules may be subsequently dried.
Granules may also be prepared by coating a core granule with an absorbent coating of filler particles. A liquid active material may then be loaded onto the surface layer of the granules. Such a process is disclosed in NZ Patent 154,193 where the objective was to produce granules with reduced absorptive properties compared to granules prepared from minerals such as attapulgite. However these granules are designed for direct application to soil, pastures or other locus and as they have cores of particle size approximately 250 μm they would not be suitable for use as WG as the granule would not pass through the spray nozzle.
Also the basic method of preparing granules involves a preliminary step of forming a wettable powder by blending the ingredients and milling them to provide the desired particle size. The wettable powder is then subsequently formed into granules by a range of techniques including agglomeration, spray drying, or other means such as pan granulation.
It is not always possible to achieve good dispersibility and shelf life with all formulations especially with compositions where the biologically active agent is in a liquid state and relatively high levels of active agent are included in the granule. There is thus a need for alternative granulation methods in order to enable a wider spectrum of liquid pesticides to be formulated in an effective and economical manner. Also there is a need for a non dusty, free flowing, storage stable solid compositions comprising pyrethroid type insecticides, more particularly semi viscous liquid pyrethroid which results in a stable dispersion in presence of water. It is well-known that the preparation of a DF formulation with liquid active using the standard inert excipients is quite difficult for over 10% active. The prior art teaches maximum of 25 EC and 25 WP for actives like Permethrin but no DF formulations exist in the market. The present invention takes care of all these problems of dry WP, solid/granular, tablet/pellets formulations given in prior art and provides for higher concentrations of liquid actives for DF formulations.